package com.hmdp.service.impl;

import cn.hutool.core.util.BooleanUtil;
import cn.hutool.core.util.StrUtil;
import cn.hutool.json.JSONObject;
import cn.hutool.json.JSONUtil;
import com.hmdp.dto.Result;
import com.hmdp.entity.Shop;
import com.hmdp.mapper.ShopMapper;
import com.hmdp.service.IShopService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.hmdp.utils.CacheClient;
import com.hmdp.utils.RedisData;
import org.omg.CORBA.PRIVATE_MEMBER;
import org.springframework.data.redis.core.StringRedisTemplate;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import javax.annotation.Resource;

import java.time.LocalDateTime;
import java.util.Random;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;

import static com.hmdp.utils.RedisConstants.*;

/**
 * <p>
 * 服务实现类
 * </p>
 *
 * @author yishun
 * @since 2023-02-18
 */
@Service
public class ShopServiceImpl extends ServiceImpl<ShopMapper, Shop> implements IShopService {
    @Resource
    private StringRedisTemplate stringRedisTemplate;
    @Resource
    private CacheClient cacheClient;

    /**
     * 根据id查询商户信息
     *
     * @param id
     * @return
     */
    @Override
    public Result queryById(Long id) {
        //缓存穿透
        //Shop shop = cacheClient.queryWithPassThrough(CACHE_SHOP_KEY, id, Shop.class, ID -> getById(id), CACHE_SHOP_TTL, TimeUnit.MINUTES);
        //互斥锁解决缓存击穿
        //Shop shop = queryWithMutex(id);

        //逻辑过期解决缓存击穿
        Shop shop = cacheClient.queryWithLogicalExpire(CACHE_SHOP_KEY,id,Shop.class,this::getById,20L,TimeUnit.SECONDS);
        if (shop == null) {
            return Result.fail("店铺不存在");
        }
        //返回
        return Result.ok(shop);
    }

    private static final ExecutorService CACHE_REBUILD_EXECUTOR = Executors.newFixedThreadPool(10);


    public Shop queryWithLogicalExpire(Long id) {//逻辑过期，解决缓存击穿
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isBlank(shopJson)) {
            return null;
        }
        //4.命中，需要判断过期时间，先把Json反序列化为对象
        RedisData redisData = JSONUtil.toBean(shopJson, RedisData.class);
        Shop shop = JSONUtil.toBean((JSONObject) redisData.getData(), Shop.class);
        LocalDateTime expireTime = redisData.getExpireTime();
        //5.判断是否过期
        if (expireTime.isAfter(LocalDateTime.now())) {
            //5.1未过期，直接返回
            return shop;
        }
        //5.2已过期，需要缓存重建
        //6.缓存重建
        //6.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        //6.2判断是否获取锁成功
        boolean isLock = tryLock(lockKey);
        if (isLock) {
            //6.3成功，开启独立线程，实现缓存重建
            CACHE_REBUILD_EXECUTOR.submit(() -> {
                try {

                    //this.savaShop2Redis(id, 20L);
                    this.savaShop2Redis(id, 1200L);
                } catch (Exception e) {
                    throw new RuntimeException(e);
                } finally {
                    //释放锁
                    unlock(lockKey);
                }
            });

        }
        //6.4返回过期商铺信息
        return shop;
    }

    public Shop queryWithMutex(Long id) {//解決緩存击穿，热点key问题，互斥锁
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中的值是否为空值
        if (shopJson != null) {
            return null;
        }
        //4.实现缓存重建
        //4.1获取互斥锁
        String lockKey = LOCK_SHOP_KEY + id;
        Shop shop = null;
        try {
            boolean isLock = tryLock(lockKey);
            //4.2判断是否获取成功
            if (!isLock) {
                //4.3失败，休眠重试
                Thread.sleep(50);
                return queryWithMutex(id);
            }
            //4.4成功，根据id查询数据库
            shop = getById(id);
            //模拟重建延迟
            Thread.sleep(200);
            //5.数据库不存在，返回错误
            if (shop == null) {
                //解决缓存穿透问题，将空值写入redis
                stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
                return null;
            }
            //6.存在，写入redis
            Random rand = new Random();
            stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL + rand.nextInt(5), TimeUnit.MINUTES);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        } finally {
            //7.释放互斥锁
            unlock(lockKey);
        }
        //8.返回
        return shop;
    }

    public Shop queryWithPassThrough(Long id) {  //緩存穿透，緩存空值 ” “
        String key = CACHE_SHOP_KEY + id;
        //1.从redis查询商户缓存
        String shopJson = stringRedisTemplate.opsForValue().get(key);
        //2.判断是否存在
        if (StrUtil.isNotBlank(shopJson)) {
            //3.存在，直接返回
            return JSONUtil.toBean(shopJson, Shop.class);
        }
        //判断命中的值是否为空值
        if (shopJson != null) {
            return null;
        }
        //4.不存在，根据id查询数据库
        Shop shop = getById(id);
        //5.数据库不存在，返回错误
        if (shop == null) {
            //解决缓存穿透问题，将空值写入redis
            stringRedisTemplate.opsForValue().set(key, "", CACHE_NULL_TTL, TimeUnit.MINUTES);
            return null;
        }
        //6.存在，写入redis
        Random rand = new Random();
        stringRedisTemplate.opsForValue().set(key, JSONUtil.toJsonStr(shop), CACHE_SHOP_TTL + rand.nextInt(5), TimeUnit.MINUTES);
        //7.返回
        return shop;
    }

    private boolean tryLock(String key) {
        Boolean flag = stringRedisTemplate.opsForValue().setIfAbsent(key, "1", 10, TimeUnit.SECONDS);
        return BooleanUtil.isTrue(flag);
    }

    private void unlock(String key) {
        stringRedisTemplate.delete(key);
    }


    /**
     * 封装逻辑过期时间
     *
     * @param id
     * @param expireSeconds
     */
    public void savaShop2Redis(Long id, Long expireSeconds) {
        //1.查询店铺数据
        Shop shop = getById(id);
        //模拟缓存重建延迟
        try {
            Thread.sleep(200);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
        //2.封装逻辑过期时间
        RedisData redisData = new RedisData();
        redisData.setData(shop);
        redisData.setExpireTime(LocalDateTime.now().plusSeconds(expireSeconds));
        //3.写入redis
        stringRedisTemplate.opsForValue().set(CACHE_SHOP_KEY + id, JSONUtil.toJsonStr(redisData));
    }

    /**
     * 更新商户
     *
     * @param shop
     * @return
     */
    @Override
    /*
        单体项目，缓存和数据库操作在一个方法，事务控制原子性
        分布式系统TTC控制
     */
    @Transactional
    public Result update(Shop shop) {
        Long id = shop.getId();
        if (id == null) {
            return Result.fail("店铺id不能为空");
        }
        //缓存更新策略：删除缓存而不是更新缓存
        //1.先更新数据库（先数据库，再缓存，线程安全问题小）
        updateById(shop);
        //2.再删除缓存
        stringRedisTemplate.delete(CACHE_SHOP_KEY + shop.getId());
        return Result.ok();
    }
}
